1. Field of the Invention
This invention relates to an apparatus and method for automatic packaging, particularly for modified atmosphere packaging, in which a load of poultry, produce or the like is inserted into a plastic bag, air is drawn out of the bag and a gas is injected into the bag, and then the plastic bag is heat sealed to form a gas-tight seal. This invention also relates to the particular plastic bag or flexible pouch associated with the apparatus and method for automatic packaging.
2. Description of Prior Art
Conventional apparatuses exist for feeding plastic sheets or plastic bags over a conveyor belt. Conventional apparatuses also exist for heat sealing plastic bags. However, when a probe or snorkel is inserted into a plastic bag and then withdrawn, in conventional apparatuses, the plastic bag has a tendency to lose pressure, particularly vacuum pressures, in the process of advancing to a heat sealing station since the two webs of the plastic bag cannot be held together as the plastic bag is transferred from a fluid transfer station to a heat sealing station.
In conventional apparatuses, a plastic bag is typically held in one position while it is loaded, a probe or snorkel is inserted into the bag to draw a vacuum in the bag, the probe or snorkel is extracted, and the bag is heat sealed. In order to reduce the amount of time and labor necessary to vacuum package products, an automatic packaging apparatus and method are needed in which a plastic bag is transferred from one position to a downline position for the loading, fluid transfer and heat sealing steps.
U.S. Pat. No. 3,359,703 discloses an apparatus for making and filling a series of bags. A series of bags are fed by driven belts, the drive of which stops when the bag reaches a filling device. A narrow wedge is placed behind a separating element for opening each bag at its upper edge. Behind the wedge, a tube which is connected to an air supply source is used to blow air into the bag and thus open the bag. Simultaneously, a subatmospheric pressure is applied to a pair of suction pads on both sides of the film of the bag, under the filling device, so that the walls of the bag are sucked against such pads. The suction pads move outwards, so that the bag is rapidly opened. Once the filling of the bag begins, the air supply and the vacuum in the suction pads are interrupted. The '703 patent neither teaches nor suggests either a snorkel or probe for injecting a gas into or drawing a gas from the plastic bag or means for maintaining a gas-tight seal upon the bag as it is transferred from such fluid transfer station to a heat sealing station.
U.S. Pat. No. 2,281,187 teaches a machine and method for packing commodities into individual and non-continuous plastic bags. A spout is inserted into a mouth of a bag which is positioned immediately beneath the spout in order to apply suction and draw a fluid from the bag. An inert gas is then injected into the bag. The '187 neither teaches nor suggests either a continuous sheet having a plurality of plastic bags or maintaining a gas-tight seal on the bag as it is automatically transferred from a gas transfer station to a heat sealing station.
U.S. Pat. No. 3,430,414 discloses a machine for packaging articles in a controlled atmosphere. A resilient sealing pad is secured to a front carrier to travel with the bags along their paths, at a sealing station. The carriers are two endless chains positioned side-by-side in a common, horizontal plane. The chains are driven at the same speed as a bag carrier to move the pads at the speed of the bags. The '414 patent also teaches individual and non-continuous plastic bags which are filled and then moved to a fluid transfer station. The '414 patent does not disclose maintaining a gas-tight seal on the plastic bags as they are transferred from a gas transfer station to a heat sealing station.
U.S. Pat. No. 3,688,463 relates to a vacuum packaging system wherein flaps are plowed open to assist in automatically filling the bags without need for probes, spreaders or the like to open the bags for evacuation purposes. U.S. Pat. No. 2,863,267 teaches an air extractor and sealing device used to extract air from commodity packed containers and hermetically sealing such packed containers. U.S. Pat. No. 2,410,834 teaches a machine for sealing bags after air has been removed from the bags. V-shaped belts are used to transport the bags from air removing means to bag sealing means.
U.S. Pat. No. 2,753,671 discloses a machine for vacuum packaging foods or commodities in flexible sheet material of a type which can be heat sealed. The machine has different working stations at which operations are simultaneously performed on a series of packages, so that one or more units can be worked on at each station at all times during settled operation of the machine.
U.S. Pat. No. 4,969,310 teaches a packaging machine and method for loading bags which are interconnected at the side of the bags. The '310 patent teaches an articulated arm for rupturing interconnections of the bags.
U.S. Pat. No. 4,730,439 teaches a method and apparatus for packaging a product in individual vacuum sealed packets. A sheet of flexible packaging material is formed into a channel-shaped member having spaced apart vertical side walls. A predetermined amount of flowable product is introduced into each of the open top packets. The upper corner portions of each individual packet are sealed to reduce the size of the opening in the packets. A vacuum tube is introduced into the open top packet and the upper portion of the open top packet is sealed around the vacuum tube. The vacuum tube is then retracted and a final horizontal top seal is produced above the initial top seal.
U.S. Pat. No. 4,021,283 teaches a method of making aseptic packaging which is free of pathogenic microorganisms. The bags are filled with a sterile product and sealed without exposing the contents of the bags to ambient air which would destroy the sterile interiors of the bags.
U.S. Pat. No. 3,751,875 discloses an apparatus having two sprocket wheels for advancing a strip of interconnected bags that are filled, sealed and dispensed. The strip of bags has spaced sprocket apertures in an edge portion of the strip. The apertures are engaged by sprockets on the sprocket wheel to linearly move the strip of bags.